Detailed revision/study notes on the entire of EQ2 Water. Includes Edexcel Geography A level Specification with detailed notes to match. Also includes case study details.
Geography Consolidation 5.4
DEFICITS WITHIN THE HYDROLOGICAL CYCLE RESULT FROM PHYSICAL PROCESSES BUT CAN
HAVE SIGNIFICANT IMPACTS
a) The causes of drought, both meteorological and hydrological
- There are many types of Drought:
- Meteorological Drought : Shortfalls of precipitation as a result of short term variability within
longer term averages -Example : Sahel
- Hydrological Drought : Drought associated with reduced stream flow and groundwater levels
because of reduced precipitation and high evaporation
- Agricultural Drought: The decrease in soil moisture and soil water available has a knock on
effect on plant growth and reduces biomass
- Famine Drought : A humanitarian crisis in which widespread famine of agriculture leads to food
shortages and wide famine
- Physical Factors for Drought :
- Natural Variability in climate can cause temporary declines in rainfall causing stores to not be
replenished
- Higher temperatures lead to increased evaporation reducing amount of water available
- Climate effects precipitation but the dynamics of this are only partially understood
- ENSO - The El Niño - Southern Oscillation
- El Nino can trigger very dry conditions throughout the world - especially South East Asia,
India, eastern Australia, south-east USA, central America and north east Brazil
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b) The contribution human activity makes to the risk of drought
- Factors increasing vulnerability to DESERTIFICATION:
- Overpopulation and increase of wealth : leads to an increased demand for water
- Overgrazing: Increased need for livestock- creates soil depletion and the land is stripped of
its protective grass cover meaning vegetation cannot re-establish itself
- Overcultivation: Farming and ploughing - this reduces soil fertility and means the soil is
exposed and eroded
- Deforestation: Removes the vegetation increasing soil erosion
c) The impacts of drought on ecosystem functioning and the resilience of these
ecosystems
- Wetland = An area of marsh, fen, peatland or water where water is static of flowing and wither
fresh or salt
- Wetlands cover 10% of the Earths surface and are very important as they perform many key
functions:
- Act as temporary water stores: reducing flood risk down stream and recharge aquifers
- Water filters : they trap and recycle nutrient and pollutants help maintain water quality
- High biological productivity : they have a very diverse food web - good for fish and birds
- Storage of Carbon: Peat acts as a carbon storage
- All these functions contribute towards their value for human society
- Drought impact on wetlands :
- Wetlands become less functional
- Also impacts due to exploiting them for resources such as peat
- Dams can also harm wetlands
- Recently many schemes have developed to protect wetlands on many different scales
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